Contactless Payment Signet Ring - Built With Coil on Chip - Chip With Built in NFC Antenna.

UPDATE - I made a new ring with an even smaller antenna and some high tech science! Check it out here!

Did you try to build the awesome ring that pockybum522 made?

Did your chip look like the above picture so there was no way to solder it?

Then this guide is for you!

I'm truly sorry guys, the list of materials needed seems to have vanished - So here it is again!

• Acetone - For melting the card. (Have a look at the final step, "Thoughts And Thanks" for other methods).
• Copper magnet wire, i used the 0.05mm.
• Glue stick, - So the wire and chip stick on the ring.
• An Android phone or tablet with NFC the app Credit card reader - For testing out the chip and ring.

Optional

• A pair of tweezers - They just make life easier!

My bank won't allow me to have more than one card tied to an account. So i had to create a second account and order a card for that one. Fortunately everything was made in the banks app and only cost $20 extra per year.

The reason this step is in all CAPS..

Well, in my eagerness to get started with the first proof of concept ring..

I forgot to do everything..

So I just ripped open the envelope that the card came in, took the card and melted it in acetone..

So, take a step back and take a deep breath.

If your bank, like mine, won't activate the card before you buy something with the chip and PIN, buy something with the chip and PIN.

Take a photo on the front and back of your card, make sure to get the card number, expiration date and CVC2/CVV2 code. Save that photo somewhere safe.

• Pour the acetone in glass container - don't breath in the acetone fumes.
• Put the card in the glass container.
• Put a lid on the glass container so the acetone don't vaporize.

I'm using a "lid" of metal, maybe I'm being over cautious, but i don't want to melt the lid.

After 45 - 60 minutes, remove the card from the glass container, bend the card carefully near the chip and remove the chip from the card. If the chip won't come loose, give it 15 more minutes in the acetone bath.

Carefully remove the glue on the backside of the chip with some paper.

Congratulations!

The hard part is done!

You can actually test the chip with the Credit Card Reader app right now, to see that it works and to figure out where the NFC antenna is on your Android device.

Unfortunately the signal is to weak or have the wrong frequency to be used as payment, for now!

With the tweezers take some stick glue and apply it on the back side of the ring. Press down the wire in the glue and start turning.

Important note: The wire needs to be on the far left or right long side of the chip. It can't be centered under or over the chip. If it's centered the antenna won't "talk" to the chip.

Since antenna building isn't an exact science..

Well, that's a lie, it is absolutely an exact science..

Rather, since I don't have access to an oscilloscope or spectrum analyzer, trial and error is the way forward.

So after A LOT - A LOT of ye olde trail and error i came to the conclusion to start with 20 turns, use some glue to hold the wire in place, put some more glue in the signet to hold the chip in place and try to read it with the Credit Card Reader app.

The trick here is to get the Android device to read the ring from both sides. not the top/signet and bottom but the sides of the ring, for me it read from both sides at 15 turns.

So if it can't read from both sides, remove one turn, try again and again until you can read from both sides.

Pro tip: Write down how many turns you try and when the ring can be read from both sides. You might wan't to make another ring and then you don't have to trial and error your way to a working ring again.

I had a payment terminal laying around, so I used that to see if the ring actually worked, and it did!

But, in my experience payment terminals like the one in the picture are really forgiving, meaning that it's probably better to try the ring in the wild.

As you can see on the picture to the right I used electrical tape over the ring to give it a "nice" glossy finish.

• What to do if the ring dosen't work in the wild?

Make sure that it can be read by an Android device from both sides, if it can't, try to remove another turn and try it in the wild again.

• Where did you put the chip, on the wire next to or under?

As I mentioned before i have worked A LOT on this project and tried hundreds of different configurations. And I can honestly tell you that I haven't noticed any change in success by having the chip over/under or next to the wire as long as it's on the far left or right long side of the chip. In the picture above the chip is next to the wire.

• Can i use a different wire?

Damn right you can, i have used 0.05mm and 0.1mm wire. The 0.1mm wire is more sturdy and won't snap as easy. But notice that there probably will be less turns with a 0.1mm wire.

• Can i use something else that acetone to get the chip out?

Since there is nothing to save from the card except the chip you could probably use a hot air gun or hair dryer to remove the chip or, as mentioned in the comments, even some scissors to cut the chip out from the card and then melt away the chip from the plastic.

There was also a comment regarding this project on Hack a day making an excellent point. Some banks might force you to use the chip and card in a payment terminal once in a while. As an extra security measure. If that's the case, you could:

1. Try the hair dryer method to remove the chip and reinsert it in the card again with some glue.
2. Use a 3D-printer or even a CNC to print out a "new" card and glue the chip to it.
3. Buy an awesome metal card or a plastic version.

And when you made the transaction with the chip, put it back in the ring. Since the chip isn't soldered it's a breeze!

And again, a big thank you to pockybum522 for making the OG NFC payment ring and to Andey for helping me making a really nice ring based on prototypes and hand drawn sketches.

Buy me a coffee? a NanoVNA to update this guide with insights of the coil on chip frequency and the best antenna design to get maximum range when reading the ring from a payment terminal.